From reading some of the other articles about this, it seems like it was Nascar's decision to take Chicagoland Speedway off the schedule. However, back in May there was a lot of discussion about the property being sold and reconfigured. Maybe NASCAR just felt they couldn't get a commitment from ownership on future development and they apparently wanted to reduce the number of 1.5-2 mile tracks anyway.
NASCAR owns the track, When it was a publicly held company, ISC , The France family had majority control, They sold all of their tracks to NASCAR in a stock buy. Sort of like just moving your money from your right hand to your left hand.
The drag strip was built by Indycar Owner Dale Coyne then sold to ISC.